In a wireless communications system, for example, a Long Term Evolution (LTE) system or a Long Term Evolution Advanced (LTE-Advanced) system, in order to directly provide a subscriber with a short message service (SMS) through an LTE network, the 3rd Generation Partnership Project (3GPP) defines a feature of a mobility management entity (MME) supporting a short message service, namely, an SMS in MME service. With this feature, when a user equipment (UE) initiates a combined attach request or a combined update request that carries SMS only indication information, an MME requests a home subscriber server or home location register (Home Subscriber Server or Home Location Register, HSS/HLR) to register the MME as a node that provides a short message service, and after the MME is registered by the HSS/HLR as the serving node that provides a short message service for a subscriber, the MME is directly connected to a short message service center SMS-SC (service center) or a short message gateway SMS-GMSC (gateway mobile switching center), and provides the short message service for a subscriber through a packet switched (PS) domain, without the need to establish an SGs association with a mobile switching center (MSC) to provide the short message service for a subscriber through a circuit switched (CS) domain.
However, in the prior art, when a combined attach request or a combined update request initiated by a user equipment does not carry SMS only indication information, an MME blindly requests an HSS/HLR to register the MME as a serving node that provides an SMS for a subscriber, which causes extra signaling interaction between the MME and the HSS/HLR when the registration is inaccurate.